The Nature Of Time Geometry Physics And Perception Pdf

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14 Patterns of Biophilic Design

We use experiments, theory and computation to study motion and matter at the human scale. Areas of interest include the patterns of shape and flow of inanimate matter in systems ranging from the supramolecular to the planetary, and the dynamics of sentient living matter that can self-organize, perceive and act in systems ranging from the sub-cellular to the super-organismal. Recent Publications. Elastic-instability enabled locomotion.

Nagarkar, W-K. Lee, D. Preston, M. Nemitz, N. Deng, G. Whitesides and L. Here we show a minimal instantiation of this principle using a thin cir- cular sheet, actuated symmetrically by a pneumatic source, using pressure to change shape nonlinearly via a spontaneous buckling instability. This leads to a polarized, bilaterally symmetric cone that can walk on land and swim in water.

In either mode of loco- motion, the emergence of shape asymmetry in the sheet leads to an asymmetric interaction with the environment that generates movement——via anisotropic friction on land, and via directed iner- tial forces in water. Scaling laws for the speed of the sheet of the actuator as a function of its size, shape, and the frequency of ac- tuation are consistent with our observations. The presence of eas- ily controllable reversible modes of buckling deformation further allows for a change in the direction of locomotion in open arenas and the ability to squeeze through confined environments——both of which we demonstrate using simple experiments.

Our simple approach of harnessing elastic instabilities in soft structures to drive locomotion enables the design of novel shape-changing ro- bots and other bioinspired machines at multiple scales.

Static adhesion hysteresis in elastic structures. Memet, F. Hilitski, Z. Dogic and L. Using this model we quantify hysteresis in terms of the adhesion and elasticity parameters of the system. This allows us to derive a scaling relation that preserves hysteresis at different levels of granularity while resolving a seeming paradox of lattice trapping in the continuum limit of a discrete fracture process.

Finally, to verify our theory, we use new experiments to demonstrate and measure adhesion hysteresis in bundled microtubules. Self-organized biotectonics of termite nests. Heyde, L. Guo, C. Jost, G. Theraulaz and L. Each nest has several characteristic structural motifs that allow for efficient ventilation, cooling, and traversal.

We use tomography to quantify the nest architecture of the African termite Apicotermes lamani, consisting of regularly spaced floors connected by scattered linear and helicoidal ramps. To understand how these elaborate structures are built and arranged, we formulate a minimal model for the spatiotemporal evolution of three hydrodynamic fields—mud, termites, and pheromones— linking environmental physics to collective building behavior using simple local rules based on experimental observations.

We find that floors and ramps emerge as solutions of the governing equations, with statistics consistent with observations of A. Our study demonstrates how a local self-reinforcing biotectonic scheme is capable of generating an architecture that is simultaneously adaptable and functional, and likely to be relevant for a range of other animal-built structures. Models for benthic bipedalism. Giardina and L. Mahadevan , Royal Society - Interface 18 : , Inspired by recent evidence of the neural underpinnings of primitive aquatic walking in the little skate Leucoraja erinacea, we introduce a theoretical model of aquatic walking that reveals robust and efficient gaits with modest requirements for body morphology and control.

The model predicts undulatory behaviour of the system body with a regular foot placement pattern, which is also observed in the animal, and additionally predicts the existence of gait bistability between two states, one with a large energetic cost for locomotion and another associated with almost no energetic cost.

We show that these can be discovered using a simple reinforcement learning RL scheme. Overall, our study highlights the physical constraints on the evolution of walking and provides a guide for the design of efficient biomimetic robots. Control of connectivity and rigidity in prismatic assemblies. Choi, S. Chen and L. Mahadevan , Proc. A , To answer this question in a deterministic setting, we use ideas from elementary number theory to provide a hierarchical deterministic protocol for the control of rigidity and connectivity.

We then show that it is possible to also use a stochastic protocol to achieve the same results via a percolation transition.

Together, these approaches provide scale-independent algorithms for the cutting or gluing of three-dimensional prismatic assemblies to control their overall connectivity and rigidity. Mechanical coupling coordinates the co-elongation of axial and paraxial tissues in avian embryos. Xiong, W. Ma, B. Mahadevan , and O. How developmental programs adapt to or take advantage of these effects remains poorly explored.

Here, using a combination of live imaging, modeling, and microsurgical perturbations, we show that the axial and paraxial tissues in the forming avian embryonic body coordinate their rates of elongation through mechanical interactions. First, a cell motility gradient drives paraxial presomitic mesoderm PSM expansion, resulting in compression of the axial neural tube and notochord; second, elongation of axial tissues driven by PSM compression and polarized cell intercalation pushes the caudal progenitor domain posteriorly; finally, the axial push drives the lateral movement of midline PSM cells to maintain PSM growth and cell motility.

These interactions form an engine-like positive feedback loop, which sustains a shared elongation rate for coupled tissues. Our results demonstrate a key role of inter-tissue forces in coordinating distinct body axis tissues during their co-elongation. Flow-driven branching in a frangible porous medium.

Derr, D. Fronk, C. Weber, A. Mahadevan, C. Rycroft and L. Mahadevan , Phys. We provide a simple theoretical framework that embodies this feedback mechanism in a multiphase model for flow through a frangible porous medium with a dynamic permeability. Numerical simulations of the model show the emergence of branched networks whose topology is determined by the geometry of external flow forcing.

Coordinated crawling via reinforcement learning. Mishra, W. It requires coordinated contractions that propagate along a body that interacts frictionally with its environment. We propose a simple approach to understand how this coordination arises in a neuromechanical model of a segmented, soft-bodied crawler via an itera- tive process that might have both biological antecedents and technological relevance.

Using a simple reinforcement learning algorithm, we show that an initial all-to-all neural coupling converges to a simple nearest-neighbour neural wiring that allows the crawler to move forward using a localized wave of contraction that is qualitatively similar to what is observed in Drosophila melanogaster larvae and used in many biomimetic solutions.

The resulting solution is a function of how we weight gait regularization in the reward, with a trade-off between speed and robustness to proprioceptive noise. Overall, our results, which embed the brain—body—environment triad in a learning scheme, have relevance for soft robotics while shedding light on the evolution and development of locomotion. Mechanical basis for fibrillar bundle morphology. Michaels, E. Memet, and L. Mahadevan, Soft Matter , 16 , , Here, we propose a coarse-grained approach that averages over specific molecular details and yields an effective mechanical theory for the spatial complexity of self-assembling fibrillar structures that arises due to the competing effects of the bending and twisting elasticity of individual filaments and the adhesive interactions between them.

We show that our theoretical framework accounting for this allows us to capture a number of diverse fibril morphologies observed in natural and synthetic systems, ranging from Filopodia to multi-walled carbon nanotubes, and leads to a phase diagram of possible fibril shapes. We also show how the extreme sensitivity of these morphologies can lead to spatially chaotic structures. Together, these results suggest a common mechanical basis for mesoscale fibril morphology as a function of the nanoscale mechanical properties of its filamentous constituents.

Optimal control of aging in complex networks E. Sun, T. Michaels, and L. This naturally raises the question of how to maximize health and longevity in an aging system at minimal cost of maintenance and intervention.

Here, we pose this question in the context of a simple interdependent network model of aging in complex systems and show that it exhibits cascading failures. We then use both optimal control theory and reinforcement learning alongside a combination of analysis and simulation to determine optimal maintenance protocols. These protocols may motivate the rational design of strategies for promoting longevity in aging complex systems with potential applications in therapeutic schedules and engineered system maintenance.

Recent Press. Harvard John A.

The Nature of Time: Geometry, Physics and Perception (NATO ARW)

We use experiments, theory and computation to study motion and matter at the human scale. Areas of interest include the patterns of shape and flow of inanimate matter in systems ranging from the supramolecular to the planetary, and the dynamics of sentient living matter that can self-organize, perceive and act in systems ranging from the sub-cellular to the super-organismal. Recent Publications. Elastic-instability enabled locomotion. Nagarkar, W-K. Lee, D. Preston, M.


The Nature of Time: Geometry, Physics and Perception Digitally watermarked, DRM-free; Included format: PDF; ebooks can be used on all reading devices.


René Descartes

Thomas Hobbes is rightly regarded as a monumental figure in the history of philosophy, especially for his masterpiece Leviathan in English; in Latin. The scholarly literature on Leviathan is voluminous and has been especially focused upon issues in political philosophy, such as representation and authorization, sovereignty and absolutism, contracts and covenants, and the relationship of civil authority to religion, among others. Hobbes [ ]. Thus, understanding his general views about the nature of scientific demonstration promises to shed light on the way in which he saw civil philosophy as scientific. This may seem like a banal claim to a twenty-first century reader, but it was not so to many in the sixteenth and seventeenth centuries.

In natural philosophy, he can be credited with several specific achievements: co-framer of the sine law of refraction, developer of an important empirical account of the rainbow, and proposer of a naturalistic account of the formation of the earth and planets a precursor to the nebular hypothesis. More importantly, he offered a new vision of the natural world that continues to shape our thought today: a world of matter possessing a few fundamental properties and interacting according to a few universal laws. This natural world included an immaterial mind that, in human beings, was directly related to the brain; in this way, Descartes formulated the modern version of the mind—body problem. In metaphysics, he provided arguments for the existence of God, to show that the essence of matter is extension, and that the essence of mind is thought.

Biophilic design can reduce stress, enhance creativity and clarity of thought, improve our well-being and expedite healing; as the world population continues to urbanize, these qualities are ever more important. Theorists, research scientists, and design practitioners have been working for decades to define aspects of nature that most impact our satisfaction with the built environment. Biophilia in Context looks at the evolution of biophilic design in architecture and planning and presents a framework for relating the human biological science and nature. Design Considerations explores a sampling of factors e.

The illusion of Gravity

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It seems that you're in Germany. We have a dedicated site for Germany. Editors: Buccheri , R. There are very few concepts that fascinate equally a theoretical physicist studying black holes and a patient undergoing seriolls mental psychosis. Time, undoubtedly, can well be ranked among them. For the measure of time inside a black hole is no less bizarre than the perception of time by a schizophrenic, who may perceive it as completely "suspended," "standing still," or even "reversing its direction. This, perhaps, since the concept entails multifarious, and occasionally incongruous, facets.

Есть математическая гарантия, что рано или поздно ТРАНСТЕКСТ отыщет нужный пароль. - Простите. - Шифр не поддается взлому, - сказал он безучастно. Не поддается. Сьюзан не могла поверить, что это сказал человек, двадцать семь лет работавший с шифрами. - Не поддается, сэр? - с трудом произнесла.  - А как же принцип Бергофского.

Разум говорил ему, что Стратмор должен быть не наверху, а внизу. Однако звук повторился, на этот раз громче. Явный звук шагов на верхней площадке. Хейл в ужасе тотчас понял свою ошибку. Стратмор находится на верхней площадке, у меня за спиной. Отчаянным движением он развернул Сьюзан так, чтобы она оказалась выше его, и начал спускаться.

Он почувствовал, как вокруг него выросла стена, и понял, что ему не удастся выпутаться из этой ситуации, по крайней мере своевременно. И он в отчаянии прошептал ей на ухо: - Сьюзан… Стратмор убил Чатрукьяна. - Отпусти ее, - спокойно сказал Стратмор.

Когда он найдет копию ключа, имевшуюся у Танкадо, оба экземпляра будут уничтожены, а маленькая бомба с часовым механизмом, заложенная Танкадо, - обезврежена и превратится во взрывное устройство без детонатора. Сьюзан еще раз прочитала адрес на клочке бумаги и ввела информацию в соответствующее поле, посмеялась про себя, вспомнив о трудностях, с которыми столкнулся Стратмор, пытаясь самолично запустить Следопыта. Скорее всего он проделал это дважды и каждый раз получал адрес Танкадо, а не Северной Дакоты. Элементарная ошибка, подумала Сьюзан, Стратмор, по-видимому, поменял местами поля информации, и Следопыт искал учетные данные совсем не того пользователя. Она завершила ввод данных и запустила Следопыта.

Бринкерхофф с облегчением вздохнул: - Ну, если он здесь, то нет проблем, верно. Мидж задумалась.

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